Remote tire monitoring systems (“RTMSs”) are known in the art. Such systems typically include a plurality of sensor units or transmitters associated with the tires of a vehicle (“tire sensors”), such as an automobile, truck, or other wheeled vehicle, along with a receiving unit. The sensors measure a tire characteristic, most commonly the air pressure in the associated tire, and communicate data corresponding to the tire characteristic to the receiving unit on the vehicle. The data is typically communicated to the receiving unit via radio frequency (“RF”) signals. The RF signals can be modulated and encoded to transmit data such as tire pressure, unique identifier, etc. The receiver typically takes some action in response to receiving the transmitted data, such as providing an alarm or providing a display to the operator of the vehicle indicative of the tire characteristic. Thus, if the air pressure in a tire is too low (or too high), the RTMS tire sensor detects the low air pressure and signals to the RTMS receiving unit, which then indicates to the operator of the vehicle which tire has the low air pressure.
In order for the receiver to reliably indicate the tire characteristic to the vehicle operator, the receiver preferably associates the tire sensor (and therefore, the tire characteristic data) with a tire position on the vehicle. This association is made upon initial installation of tires on the vehicle and must be repeated each time tire positions are changed, such as after tire rotation, or a new tire is installed.
A technician installing new tires on a vehicle or changing the positions of tires (that is, rotating tires) on a vehicle can program the vehicle's RTMS receiving unit to associate the tires on the vehicle with their tire positions by first putting the receiving unit into learn mode or programming mode and then activating the tire sensors in a sequence specified by the manufacturer of the RTMS receiving unit. The methods for putting receiving units into programming mode are typically manufacturer dependent, but are generally known in the ant. For example, it is known in the art that some RTMS receiving units manufactured by Ford Motor Company can be put into programming mode by first turning the ignition on (not in start position) and off three times, followed by depressing the vehicle's brake, followed by again turning the ignition on and off three times.
Once the receiving unit is placed into programming mode it will expect the tire sensors to be activated in a particular sequence. That is, the receiving unit may expect the tire sensor in the right front tire to be activated first, followed by the tire sensor in the left front tire, etc. The precise sequence for activating tire sensors is determined by and readily available from the manufacturer of the RTMS.
As each tire sensor is activated, it transmits a signal (“tire sensor signal”) to the receiving unit. The tire sensor signal will typically contain a unique ID that identifies the particular tire (that is, tire sensor) that is transmitting the tire sensor signal. The receiving unit associates this unique ID with the position of the tire from which the signal is being transmitted. In this manner, the receiving unit learns the position of each tire as it is being activated. After each tire is activated, the receiving unit will typically emit a sound, such as a beeping sound, to indicate to the technician that the receiving unit received a tire sensor signal from the activated tire and that the next tire in the sequence can be then activated.
At any later point in time when a tire sensor is activated, it transmits its unique ID along with pertinent data about the tire (such as tire pressure, for example) and the receiving unit can then display the transmitted data as necessary to the operator of the vehicle, also indicating the tire position to the operator. For example, if while a vehicle is in operation the right front tire starts losing air pressure, the loss of air pressure is detected by the tire sensor in the right front tire, the tire sensor transmits the tire pressure to the receiving unit (along with its unique ID), the receiving unit determines the tire position (that is, right front) of the transmitting tire sensor from the previous association of unique ID to tire position and then indicates to the operator of the vehicle that the right front tire has low tire pressure.